NATO Secretary General Jens Stoltenberg, US Defense Secretary Lloyd Austin (L) and Poland Defence Minister Mariusz Blaszczak (R) talk at the start of a round table as part of a NATO Defense Ministers' meeting over the Ukraine war at the alliance's headquarters in Brussels on March 16, 2022. (

NATO Secretary General Jens Stoltenberg, US Defense Secretary Lloyd Austin (L) and Poland Defence Minister Mariusz Blaszczak (R) talk at the start of a round table as part of a NATO Defense Ministers' meeting over the Ukraine war at the alliance's headquarters in Brussels on March 16, 2022. ( AFP via Getty Images / KENZO TRIBOUILLARD

Congress Still Needs to Protect America’s NATO Membership

Trump was closer than anyone realized to pulling the U.S. out of NATO. Lawmakers must ensure that never happens without them.

Russia’s brutal invasion of Ukraine has given the world a visceral reminder of the value of NATO. But it’s easy to forget just how close the United States recently came to quitting the alliance—and how uncertain the future of U.S. participation will remain unless Congress takes steps to protect it.

Former National Security Advisor John Bolton two weeks ago said that President Donald Trump almost withdrew the United States from NATO at the 2018 summit, over the objections of Bolton and Trump’s other senior advisors. Bolton also predicted that, had Trump been re-elected, he would likely have gone through with it.

Trump may yet get another chance, as he continues to hint that he will run for the 2024 Republican presidential nomination. Even if Trump is never re-elected, some of his political allies, and even other potential presidential candidates like Florida Gov. Ron DeSantis, have adopted a similarly skeptical or even hostile view of European alliances that might lead them to consider it.

The threat of a president pursuing NATO withdrawal over the objections of Congress and the American public is not empty. While the Constitution is silent on the issue, the mainstream legal view is that the president has the authority to withdraw the United States from treaties pursuant to their terms, without any input from Congress. Trump acted on this authority multiple times, as did several of his predecessors. Efforts to challenge these withdrawals in court have failed on technical grounds, leaving the president’s claim of authority undisturbed. 

In NATO’s case, Article 13 of the North Atlantic Treaty states that a member state may withdraw one year after its government gives notice to the United States, which would inform the other member governments. This means a future president could initiate withdrawal and complete it within a single term in office.

Congress has occasionally tried to forestall this possibility. Lawmakers have inserted into recent defense authorization bills non[-binding language expressing Congress’s continued support for NATO. Congress also prohibited the executive branch from using any appropriated funds to pursue an exit from NATO through most of Trump’s last year in office. But if it truly wants to protect NATO membership, Congress needs to put permanent legal limits on the possibility of exit. 

Congress should enact language that expressly prohibits the president from initiating withdrawal without congressional approval and prohibits any use of appropriated funds to do so. In foreign affairs, the president can often act with broad leeway where Congress is silent. But when acting contrary to Congress’s clearly expressed views, the president’s authority is constrained, especially when set out in binding legislation. Using Congress’s power over appropriations to reinforce these limits will make them even harder to ignore. 

Additionally, Congress should expressly authorize litigation on its behalf if the president pursues withdrawal. Lawmakers should also consider empowering legal action by private parties with an interest in U.S. membership in NATO, such as U.S. service-members and Americans with relatives in Europe. Both measures will maximize the chances of establishing legal standing, the main barrier that has prevented other challenges to treaty withdrawal. And the Supreme Court has suggested that other technical barriers that have hindered past legal challenges to treaty withdrawals are likely to be lower when the president is acting contrary to a statute.

The Senate Foreign Relations Committee last year passed a bill cosponsored by Sen. Tim Kaine, D-Va., that would take several of these steps, but it never received a floor vote. A new version in the current Congress, S.J. Res. 17, has 15 bipartisan cosponsors but awaits action.

Senators should not wait to act until the next presidential threat of NATO withdrawal.

Before Trump left office, the Justice Department issued a legal opinion arguing that the president can withdraw from treaties even where Congress legislates otherwise. The opinion focused on the Open Skies Treaty, from which Trump withdrew despite an advance notification requirement imposed by Congress. But a future president might rely on this same logic to similarly disregard other limits Congress has imposed on the president’s ability to end U.S. treaty relationships.

Biden administration lawyers should consider repealing or narrowing this opinion, which goes beyond the position that the Justice Department had previously taken. But even if they don’t, lawmakers shouldn’t be intimidated. Congress has strong constitutional arguments that it can limit U.S. withdrawal from NATO. Credibly threatening to litigate these issues may well be enough to deter future presidents.

Scott R. Anderson is the David M. Rubenstein fellow in governance studies at the Brookings Institution and senior editor for the online publication Lawfare. He previously served as an attorney-adviser with the U.S. Department of State and as the legal advisor for the U.S. Embassy in Baghdad, Iraq.